How to deprecation warn on all classmethods in python

warn_class_methods.py

def _warn(cls, func, *args, **kwargs):
    warn("blah_class is deprecated - use BlahClass instead", DeprecationWarning)
    return func(*args, **kwargs)


class blah_class(BlahClass):

    @classmethod
    def add_warnings(cls):
        for attr_name, attr_value in BlahClass.__dict__.items():
            if isinstance(attr_value, classmethod):
                setattr(blah_class, attr_name, partial(_warn, cls, getattr(BlahClass, attr_name)))

blah_class.add_warnings()